1. Field of the Invention
The present invention relates to a phenolic resin foam and a process for producing the same. More particularly, the present invention relates to a benzylic ether type phenolic resin foam and a process for producing the same.
2. Description of the Prior Arts
It is known that conventional phenolic resin foam exhibits excellent heat resistance and flame resistance and a low smoke-generating property. Conventional phenolic resin foam is, however, disadvantageous of its high friability and brittleness as compared with other resin foams, such as polyurethane foams and polystyrene foams. Additionally, conventional resol resin per se exhibits poor chemical stability during storage thereof, and novolak resin is difficult to handle as it is a solid. Therefore, the demand for conventional phenolic resin foam is not increasing appreciably at present.
It is also known to prepare phenolic resin foam from benzylic ether type phenolic resin. While this resin per se exhibits satisfactory stability for storage, the use of benzylic ether type phenolic resin is disadvantageous in that when it is mixed with a hardening agent, the hardening reaction proceeds at an extremely fast rate with generation of undesirable exothermic heat and bubbles. Also, the resultant foam has a low density and a high friability and, therefore, is useless as a practical heat-insulating material.
Japanese Examined Patent Publication (Kokoku) No. 55-27093 discloses a process for producing a polyurethane foam by the reaction of a benzylic ether type phenolic resin with a diisocyanate compound in the absence of a promotor. The resultant foam, however, exhibits a poorer flame-retarding property and a higher smoke-generating property than conventional phenolic resin foam.